Bad fuel mileage on 2026 1500 5.7 hemi. Highway driving

Kwilson · Apr 2, 2026

Anyone experiencing poor fuel economy at highway speeds between 70 and 75 mph?
Averages 14.5 mpg! Also rpm range is about 2300 at that speed. My other 3 trucks get almost 20 and they are 8 and 9 years old.
WTH!!!!
Help

MikeinTenn · Apr 2, 2026

2023 5.7 just finished 5k road trip averaging over 19. Headwinds, mountains, lowered it, 20+ cruising.

Other than uphill, headwind or heavy load, all I can think of is transmission didn’t shift as it should.

BTW my fuel economy falls way off at 78mph. 77 is fine but any faster and I’m losing time because of gas stops.

06 Dodge · Apr 2, 2026

Kwilson said:
Anyone experiencing poor fuel economy at highway speeds between 70 and 75 mph?
Averages 14.5 mpg! Also rpm range is about 2300 at that speed. My other 3 trucks get almost 20 and they are 8 and 9 years old.
WTH!!!!
Help

Try keeping the speeds at 70 MPH and don't say you can't I have drove in TX so know it can be done so long as your not in the left lane.....

Kwilson · Apr 2, 2026

I can baby this truck and I’m lucky if I would get 16mpg. I’ve got 3 other hemi’s and they all get 17 to 20 at hwy speeds. Anyone know much more information on the etorque?

Dan Topp · Apr 2, 2026

Dan Topp · Apr 2, 2026

I have a tuned blower truck and unloaded on a level road get 18-19 With a trailer down to 10-12 at 80 through texas

Kwilson · Apr 2, 2026

52 gallons of fuel took me 800 miles!!
That’s just crappy! Unloaded no trailer
WTH is up with this!

RamDiver · Apr 2, 2026

Kwilson said:
52 gallons of fuel took me 800 miles!!
That’s just crappy! Unloaded no trailer
WTH is up with this!

What is the mileage?

When my Hemi was new, the first 3K to 5K miles or more sucked for gas mileage.

Now the fuel economy is mostly temperature dependent and how happy my right foot gets slamming the skinny pedal.

.

crash68 · Apr 3, 2026

Kwilson said:
Also rpm range is about 2300 at that speed.

What axle ratio is the truck?
Even with 3.92 the rpm and speed don't add up close enough, even accounting for if the transmission wasn't shifting into 8th. Probably the closest ratio combination is 3.21 axle with the transmission in 6th

Dan Topp · Apr 3, 2026

06 Dodge said:
Try keeping the speeds at 70 MPH and don't say you can't I have drove in TX so know it can be done so long as your not in the left

madtrucker2016 · Apr 3, 2026

Kwilson said:
Anyone experiencing poor fuel economy at highway speeds between 70 and 75 mph?
Averages 14.5 mpg! Also rpm range is about 2300 at that speed. My other 3 trucks get almost 20 and they are 8 and 9 years old.
WTH!!!!
Help

You got a high gear ratio, I would say, not good for highway driving.

Kwilson · Apr 3, 2026

3.21 gears with 1300 miles on the truck. Guess it’s still breaking in!?
The first 750 miles on this truck was highway.

DanAR · Apr 3, 2026

Something seems wrong with those rpm’s. My 23 1500 has a 3.92 axle, 20” wheels and it’s showing exactly 2,000 rpm’s at 70 mph. I don’t think I would get up to 2300 at 75 mph. If you have 3.31 gears and even 18” wheels it shouldn’t be turning that high I don’t think. I wonder if something is keeping your transmission from shifting into 8th gear? I guess you aren’t running in tow haul mode?

Dan Topp · Apr 3, 2026

This is what 80 can look like 4/1 in liberty co. Tx A f150 sideswiped a f250 and headoned a Lincoln 3 dead.

Kwilson · Apr 3, 2026

3.21 gears in 8th gear not in tow mode. A gentleman did mention I need a few more miles on the truck before I will see the fuel mileage expected!?

runamuck · Apr 3, 2026

my '19 laramie 4x4 ccsb 5.7 with the 3.92 gears pretty much always got around 20 on the highway at 75ish.

RamDiver · Apr 3, 2026

Kwilson said:
3.21 gears in 8th gear not in tow mode. A gentleman did mention I need a few more miles on the truck before I will see the fuel mileage expected!?

I changed the oil & filter several times in the first 3K miles. Each time it was black and had lots of particulate.

I was also alarmed by the engine drag while coasting. The engine was obviously built to close tolerances and took time to break in.

The tranny temperature was insanely hot.
I recall calling the dealership twice, and they said that was expected.

I'm not positive of the exact temperature.
I switched from ⁰C to ⁰F soon after buying the truck.
IIRC, the tranny temperature was about 185⁰F.

Last night, driving home, it was 112⁰F

.

EdGs · Apr 3, 2026

2300 rpm at 70-75 mph does seem high to me, you shoukd be 1700 or so at that speed, esp. with an 8-spd.

I'm gonna have to look closer at mine tonight to make sure.

Is your ECO light on at that cruising speed?

olyelr · Apr 3, 2026

I have noticed my ‘26 hemi (with etorque obviously) does not get as good of mpg’s as my ‘17 did. The best tankful i have averaged is 17 at the most, where i was usually around 18-20 with the ‘17. That is on country 55mph roads with no stop lights.

I have been blaming it on the gears (3.92 instead of 3.21) as well as it has been winter the entire time i have owned it, so a lot of warm ups and winter gas. Ive got just under 10k miles on it now.

Im also not ruling out the etorque actually gets worse mileage, but am having a hard time proving it.

Just got back from a freeway trip last week, the rpms at 75-80 mph are around 2300-2500. Mileage was down around 15.

crash68 · Apr 3, 2026

DanAR said:
My 23 1500 has a 3.92 axle, 20” wheels and it’s showing exactly 2,000 rpm’s at 70 mph. I don’t think I would get up to 2300 at 75 mph. If you have 3.31 gears and even 18” wheels it shouldn’t be turning that high

All the regular Gen51500 trucks have the same OD tire even if the rim size is different. The Rebel, RHO and TRX have larger diameter tires

Kwilson said:
3.21 gears in 8th gear not in tow mode

While driving you can push the ERS - button then ERS + to watch what gear the transmission is reporting it's in and the what gear it's limited to.
Having 3.21 axle gears at 2300 RPMs in 8th gear you'll be going a lot faster than 70-75, more like 100 mph. Even with 3.92 you would be almost 85.

Bad fuel mileage on 2026 1500 5.7 hemi. Highway driving

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